When animals hibernate, their body temperature and metabolism drops, reducing the amount of energy they require.

This enables them to get through a long cold winter when there's no food about, and to maintain a decent body weight so they are ready to pounce into action come spring.

Past research suggests the more time animals spend hibernating, the longer they live.

But while this suggests hibernation slows the rate of ageing, the longer life span could be due to some other factor, says Turbill.

To explore this question further he and colleagues tested if hibernation affected the rate of telomere shortening in a cold temperate European rodent, which is known to rest up for up to nine months of the year in burrows under the snow in winter.

The animal they studied was the edible dormouse (Glis glis) - so named because they were once fattened up with acorns in clay pots and then eaten by the Romans, says Turbill.

Telomere shortening

Telomeres are pieces of DNA at the end of chromosomes that shorten every time a cell divides, and in response to oxidative stress.

The rate at which telomeres shorten has been shown to predict how long an animal survives, says Turbill.

In a study carried out at the University of Veterinary Medicine Vienna, he and colleagues measured the loss of body mass in the animals over winter hibernation as an index of hibernation - the lower the loss, the more they hibernated in winter.

They then used a technique called PCR to measure the change in telomere lengths in small samples taken from the dormouse.

"We measured the telomere length at the start and the end of the hibernation season," says Turbill.

"Those individuals that lost more mass over winter also hibernated less and their telomeres shortened faster."

Turbill stresses telomere shortening does not necessarily cause ageing, but if it is a measure of age, the findings add further evidence that hibernation slows ageing.

He says it's possible that hibernation reduces telomere shortening and ageing because metabolic rate, and hence all cellular processes, are slowed down.

The alternative explanation is that the hibernation state may be resistant to cellular stress, says Turbill.

Human hibernation?

While there has been a long-standing fantasy of humans hibernating so they can last the distance of space travel, Turbill says the latest findings can't shed much light on this dream.

"It's quite difficult to extrapolate data from small mammals that naturally hibernate to humans that do not hibernate naturally," he says.

Turbill emphasises hibernation is different from sleeping, which does not involve the same large drop in body temperature and metabolism.

"Sleep looks similar, but it's different," he says. "In fact hibernating mammals have to wake up to sleep."